<!--
 * @Description: This is a JS program !
 * @Author: 史志龙
 * @Github: https://github.com/szl-shalom/
 * @Date: 2019-08-22 10:25:21
 * @LastEditors: 史志龙
 * @LastEditTime: 2019-08-22 10:29:31
 -->
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>

<body>
    <script>
        var str = "123123"
        var str1 = "456"

        // var newStr = str.concat(str1)

        // console.log(str, str1, newStr)


        // var index = str.indexOf("3", 3)
        // console.log(index)
    </script>
</body>

</html>